The telephone number 9-1-1 has been designated as the universal emergency number for public use to request emergency assistance. The code 9-1-1 was chosen because it is brief, easily remembered and can be dialed quickly. FIG. 1 is a schematic diagram illustrating one example of a conventional 9-1-1 system 100. As shown, system 100 includes a user telephone 102, a telecommunications company central office 104 in telecommunication with telephone 102 over a fixed wireline telephone network (e.g., public switched telephone network (PSTN)) 106, and a public service answering point (PSAP) 108 in telecommunication with the central office. Depending on the area of service, typically a county or state, there may be one or more PSAPs. PSAP 108 functions to dispatch or transfer incoming 9-1-1 calls to the proper law enforcement, fire protection, emergency medical service or agency, etc. (collectively, “emergency service providers”) responsible for responding to the emergency. In system 100, all 9-1-1 calls originating from telephone 102 are directed to a particular PSAP 108 through central office 104, depending on the exchange (i.e., first three digits) of the calling party number (CPN). In system 100, an operator at PSAP 108 then determines the location and type of the emergency and transfers the call to the proper one of a plurality of emergency service providers ESP1, ESP2, . . . ESPn that should respond to the call.
An enhanced 9-1-1 (E-911) system has evolved from the Basic 9-1-1 system by providing an automated system for selectively routing 9-1-1 calls originating from telephone equipment at fixed address locations to the proper PSAP 108. FIG. 2 schematically illustrates an E-911 system 200 similar to system 100 described above. In E-911 system 200, telephone 102 has a telephone number TN2 and a calling party number CPN associated therewith. System 200 further includes a selective router 202 operated in association with the central office 104, and an associated selective routing database (SRDB) 204. Selective router 202 is an automated routing device that searches database 204 for a match with the particular CPN received from telephone 102. System 200 determines the primary PSAP for receiving emergency calls from the address of the subscriber of the CPN from SRDB 204.
In addition to SRDB 204, system 200 also includes emergency service numbers (ESNs) assigned to each ANI based on the customer's location as pre-validated against a master street address guide (MSAG) 206. The MSAG includes a listing of all streets and house numbers ranges within a specific 9-1-1 service area. The streets and address ranges are assigned selective routing codes, or emergency service numbers (ESNs), to enable proper routing of 9-1-1 calls. Accordingly, MSAG 206 is a summary database of valid address ranges, with the corresponding ESN for each range. Each assigned ESN is a unique number assigned to combinations of PSAP, police, fire and emergency service (EMS) providers. System 200 further includes an automatic location identifier Data Base Management System (ALI/DBMS) 208 including CPN, subscriber name, valid MSAG address information and the associated ESN. As with MSAG 206 ALI/DBMS 208 is in operatively connected to PSAP 108, MSAG 206 and SRDB 204.
In operation, 9-1-1 calls from telephone 102 are received at central office 104 and transferred to selective router 202. Selective router 202 then searches SRDB 204 for routing instructions assigned to the ESN associated with the CPN received in the incoming call. The routing instructions assigned to the ESN are associated with the telephone number of the PSAP that should receive emergency calls from the address of the subscriber of the CPN (i.e., PSAP 108). Selective router 202 then uses this telephone number to transfer the 9-1-1 call to the designated PSAP 108. Upon having the call routed to the appropriate PSAP 108 by selective router 202, PSAP 108 queries ALI/DMBS 208 to determine the name and address of the CPN subscriber and predetermined emergency service providers ESPn. This information is then displayed on a 9-1-1 PSAP operator's ALI screen.
With the increasing ubiquity of the Internet and Internet availability, there has been an increasing desire to leverage its robust and inexpensive architecture for voice telephony services, commonly referred to as voice over IP (internet protocol), or VoIP. Toward this end, standards for internet telephony have been promulgated by both the International Telecommunication Union Telecommunication Standardization Sector (ITU-T) in the form of H.323 rev 5 (2003), “Packet based multimedia communications systems” as well as the Internet Engineering Task Force (IETF) in the form of RFC 3261 (2002), “Session Initiation Protocol (SIP)” to enable set-up and teardown of the media sessions.
Unfortunately, existing VoIP offerings fail to adequately provide suitable 9-1-1 or E-911 services due mainly to the fact that originating VoIP devices, unlike conventional land line telephones, may not be associated with a specific geographical location.
Typically, in conventional local service access VoIP systems, 9-1-1 calls are not processed in the manner described above for conventional telephone calls. In some instances, VoIP 9-1-1 calls are blocked from completion. This clearly is an unacceptable option for dealing with 9-1-1 calls. In alternative systems, VoIP service providers perform dialed digit manipulation on 9-1-1 calls and replace the dialed “9-1-1” digits with a ten digit emergency services telephone number associated with the VoIP subscriber's TN and location at the time service is ordered. Unfortunately, such calls are not routed through the 9-1-1 system described above and are, therefore, not handled with the exceptional level of care and priority afforded to traditional 9-1-1 calls. Additionally, no Automatic Location Identification (ALI) information is provided to the emergency service provider along with the call.
There remains a significant need for systems and methods that support 9-1-1 call functionality for internet telephony customers who utilize VoIP in a mobile or nomadic environment.